I. FIELD OF THE INVENTION
This invention pertains to methods and devices for deflecting (i.e., at least partially separating) a sheet such as an insert, and particularly to such methods and devices as are usable in connection with collation or insertion machines of the type wherein inserts are engaged and withdrawn from an insert hopper for deposit onto an insert track for further processing.
II. PRIOR ART AND OTHER CONSIDERATION
For decades vacuum-communicating devices known as "vacuum cups" or "sucker cups" have been used to deflect sheet-like inserts from their associated hoppers in preparation for removal of the inserts from the hoppers. For example, U.S. Pat. No. 2,325,455 to Williams shows an insertion machine wherein at an insert station a lowermost insert document is deflected downwardly by a vacuum-communicating sucker cup. Sucker cups of this type, being mounted beneath their associated hopper, generally rotate upwardly toward a stack of inserts stored in the hopper; vacuum-attract an edge portion of the lowermost insert onto the cup; and, rotate downwardly away from the hopper, thereby causing an edge of the lowermost insert to be deflected downwardly with respect to the hopper floor and, therefore, at least partially separated or selected with respect to the stack of inserts in the hopper. Thereafter a separator device such as a separator foot is operated to be interposed between the deflected portion of the lowermost insert and the other inserts in the hopper. A gripper arm then engages the separated lowermost insert for removal of the insert from the hopper and for placement of the insert on an insert track or raceway.
The hoppers of prior art insert stations generally have a vertical front plate or wall from which two stripper pins typically extend horizontally into the volume defined by the hopper. While much of the surface area of a lowermost insert in such a hopper, particularly rearward portions of the lowermost insert, is supported on the hopper floor in conjunction with a breaker plate, the two stripper pins form a temporary means of at least partial support for the front edge of the lowermost insert.
Insert hoppers typically have different types of documents stored therein for different applications of an insertion machine. In this respect, the type of material stored in an insert hopper can vary from batch to batch. During one batch a sucker cup associated with a hopper may be required to deflect straight single sheets, but during another batch the sucker cup may be required to deflect sheets of any one of a plurality of possible types such as letterfolded sheets, sheets with perforated edges or sheets which are partially perforated, Z-folded sheets, edge-folded sheets, or even booklet-like signatures. The physical characteristics of inserts can also vary from batch to batch. For example, the sheets which are to be deflected by the sucker cup can be either porous, stiff, limp, thin, or thick. Moreover, during any batch a sucker cup may encounter an insert that is defective--an insert that is either misfolded, miscut, or warped, for example.
From the foregoing it is readily appreciated that sucker cups are expected to deflect inserts of varying types and varying characteristics. Therefore, in setting up each insert station in anticipation of a new batch, an operator must determine whether the sucker cup and stripper pin arrangement faces or causes any of a plurality of possible problems in deflecting inserts from the hopper.
A problem associated with the use of prior art stripper pins is that the location of the stripper pins must be adjusted to take into consideration the size of the inserts. These adjustments are generally very delicate and, if done improperly, can disrupt the feeding process. In addition, if some of the inserts at a particular station are irregularly cut or are miscut, the stripper pins may not effectively support nor reliably separate those inserts. Further, the relatively sharp stripper pins have been known to tear the front edges of some inserts during the feeding process.
One problem associated with usage of the conventional sucker cup can arise when a hopper is stacked with inserts of a porous material. The porosity of the insert can permit the vacuum to bleed through the lowermost insert and attract another insert. In order to preclude a mistaken deflecting of two inserts, parameters associated with sucker cup and stripper pin operation must be adjusted whereby the sucker cup just barely contacts the lowermost insert and rapidly rotates away.
Another problem associated with conventional sucker cups is the creation of an induced vacuum that can occur between the lowermost insert (the insert being deflected) and the next-lowermost insert. The rapid deflection of the lowermost insert at least momentarily creates a negative pressure in the region between the two inserts, with the result that the next-lowermost insert is deflected along with the lowermost insert. Creation of an induced vacuum to such an extent may result in an unacceptable "double" feed, resulting in an error condition in the operation of the insertion machine.
From the foregoing it is appreciated that in seeking to solve one problem, the prior art sucker cup devices set up yet another problem. In this regard, as prior art sucker cup devices contact and then rapidly rotate away from porous insert material in order to combat bleed-through, the rapid rotation tends to develop the undesirable induced vacuum.
To overcome the peculiar problems associated with conventional sucker cups, numerous adjustments regarding the sucker cup mechanism and the stripper pins are often made--typically by trial and error--on a station-by-station basis. The adjustments are time-consuming and unfortunately are not completely preventative. In this respect, adjustments are typically made when the machine is operated at a slow or jog speed. At jog speed the machine appears to an observer to be operating in slow motion, and the vacuum is applied through the sucker cup for a longer period of time than when the machine is operating at a higher rate of speed. Thus, the duration of the time period for which a porous insert, for example, feels the vacuum during set-up or adjustment differs from the duration of the time period during which inserts will feel vacuum when the machine is operating at a higher speed. Hence, adjustments made on the basis of conditions occurring at jog speed or upon start up are not necessarily accurate.
Devices in other environments of the sheet handling art have addressed a problem somewhat analogous to the vacuum bleed-through problem described above. Prior art attempts to solve such a problem include apparatus constructed to operate in a manner to apply Bernoulli's theorem for the attraction of an object such as a sheet, card, or wafer. The utilization of Bernoulli's theorem in this manner is discussed inter alia in U.S. Pat. Nos. 3,438,668; 3,219,340; 3,168,307; and, 3,345,922. In such apparatus a fluid such as air is directed through a tube or head essentially orthogonally to the plane of the object in a manner whereby a low pressure region is formed between a flow boundary surface of the head and the object, with the result that the object is urged by atmospheric pressure into the low pressure region, and thus attracted toward the head. It has hitherto been unrecognized, however, how devices operating on the basis of Bernoulli's theorem could be practically employed in an insertion or collation machine.
In view of the foregoing, it is an object of the present invention to provide an effective method for deflecting sheets from a hopper, and a device which operates in accordance therewith.
An advantage of the present invention is the provision of an easily operated deflecting device and method which eliminates numerous adjusments heretofore required.
Another advantage of the present invention is the provision of a deflecting device and method which properly deflects porous material sheets without deflecting "doubles" as well.
Yet another advantage of the present invention is the provision of a deflecting device and method which significantly reduces induced vacuum considerations.
A further advantage of the present invention is the provision of means which obviates the employment of prior art stripper pins and the adjustment difficulties associated therewith.